The present invention pertains to sensors and particularly to temperature sensors. More particularly, the invention pertains to resistance temperature devices.
Thermocouples produce small signals and require a cold junction for accurate temperature measurements. Thermocouples are unstable and require calibration. Thermistors have a limited range of temperature measurement because of a high temperature coefficient of resistance (TCR). Also, thermistors are not compatible with integrated circuitry. Related art resistance temperature devices (RTD""s) typically are fabricated with platinum (Pt) metal wires or films. Several disadvantages of Pt RTD""s are expensive Pt and low resistance. RTD""s using metal conductor sensing elements have low base resistances, which are difficult to measure without heating the devices, and have different performance profiles at cold and hot temperatures.
The present invention is a RTD having a hafnium (Hf) nitride (N) sensing element. This RTD has a wide temperature operating range, has a simple temperature performance profile and is compatible with silicon processing and integrated circuitry. The present RTD may be passivated with merely a silicon nitride (SiN) film. The RTD is just a two-wire device in contrast to related-art RTD""s that require three or four wires for useful measurements over a practical temperature range. The present RTD is quite manufacturable and commercially viable. This temperature sensor has application in thermal control and propulsion system monitoring of spacecraft, and for providing measurements of automotive and aircraft engines, brakes and emission control systems. The RTD also has cryogenic applications.